Statistics:Z and T Statistics: Confidence Interva
posted by Carma .
Z and T Statistics: Confidence Intervals and Significance Tests:
A friend who hears that you are taking a statistics course asks for help with a
specific chemistry lab report. She has made four independent measurements of the
specific gravity of a compound. The results are : 4.48, 4.6, 4.33 and 4.57. You are
willing to assume that the measurements are not biased. This means that the mean M of the
distribution of measurement is the true specific gravity.
4.48
4.6
4.33
4.57
a) Calculate a 95% confidence interval for the true specific gravity for your friend.
Use Table T
b) Explain to your friend what this means
Use Table T
c) What must be true about your friend's measurements for your results in part (a) to be
correct?
Use Table T
d) You notice that the lab manual says that repeated measurements will vary according to a normal
distribution with standard deviation 0=0.11. Redo the confidence interval of part (a) using this additional
information. Explain why we expect the new interval to be shorter.
Use Table Z*
e) What critical value from the table would you use for an 80% confidence interval? Without
calculating that interval would you expect it to be wider or narrower that the 95% confidence interval?
Use Table Z*
f) The lab manual also asks whether the data show convincingly that the true specific gravity is less
than 4.5. State the null hypothesis used to answer this question. Then calculate the test statistic and
find its Pvalue. Use the lab manual's value o=0.11 and calculate the pvalue in detail.
Use Table Z*
g) Explain to your friend what your pvalue means.
Use Table Z*
Respond to this Question
Similar Questions

Statistics:Significance Test and Confidence Interv
Significance Test and Confidence Intervals In General: You are reading an article in your field that reports several statistical analyses. The article says that the Pvalue for a significance test is 0.045. Ifs the significant at the … 
Statistics:Significance Test and Confidence Interv
Significance Test and Confidence Intervals In General: For another significance test, the article says that the result was significant at the 1% level. Arte such results always, sometimes, or never significant at the 5% level? 
Statistics:Significance Test and Confidence Interv
Significance Test and Confidence Intervals In General: The article contains a 95% confidence interval. Would the margin of error in a 99% confidence interval computed from the same data be less, the same, or greater? 
Statistics
Compare the 95% and 99% confidence intervals for the hours of sleep a student gets. Explain the difference between these intervals and why this difference occurs. 95% confidence intervals: 6.214, 7.686 99% confidence intervals: 5.944, … 
Statistics
Compare the 95% and 99% confidence intervals for the hours of sleep a student gets. Explain the difference between these intervals and why this difference occurs. 95% confidence intervals: 6.214, 7.686 99% confidence intervals: 5.944, … 
Statistics Math
Assume that a random sample is used to estimate a population proportion p. Find the margin of error E that corresponds to the given statistics and confidence level. n=550 x= 220, 90% confidence The margin of error E = (round to four … 
Statistics
The confidence interval below for the population variance is based on the following sample statistics: n = 25, xbar = 31.1, and s = 4.2. 9.29 < standard deviation squared < 42.82 What is the degree of confidence? 
statistics
Can someone please help me understand how confidence intervals fit within the broader context of inferential statistics 
statistics
The following list is a sampling of the costs of various statistics textbooks used at several colleges. Give the upper confidence limit for a 95% confidence interval estimate for the mean cost of all statistics textbooks. 109.95; 92.00; … 
math statistic
One of your friends knows that you are taking Advanced Placement Statistics and asks for your help wither Chemistry lab report. She has come up with five measurements of the melting point of a compound: 122.4, 121.8, 122.0, 123.0, …